The Forth Bridge/Drawings
Drawings.
All detail drawings were made at the drawing offices attached to the works and submitted to the engineers previous to being passed into the workshops. If necessary, full-size drawings were made on the blackened floor of the large drawing loft, and from these all templates were made in wood. The templates were carefully cut to size, all holes drilled in them, and all necessary information and description branded upon the template in clear type. In certain cases, such as bracing bars, which recur several hundred times over, some of the bars themselves were used as templates. For the erection of the superstructure the tracings were transferred to sheets prepared by the ferro-prussiate process, by which the only part of the paper remaining white is that which underlies the full or dotted lines of the tracings. The drawing is, therefore, of white lines upon a deep blue ground.